The invention relates to a vibrating screen centrifuge for dewatering fine-grained material comprising two vibrating and rotating work masses which are placed in vibration with a phase shift of 180.degree. in an axial direction.
Vibrating screen centrifuges are especially employed for dewatering fine-grained materials, such as coal, salts and sands. Single-mass and dual-mass sympathetic vibration systems comprising screen basket diameters up to about 1300 mm are known for this purpose. In the single-mass system, however, vibrating weights of about 1000 kg derive given a screen basket diameter of 1300 mm, these weights leading, for example, given 10 g axial acceleration, to bearing loads of about 10 t which must be absorbed both by the main bearings as well as by the unbalance bearings. An increase of the axial acceleration to about 20 g in order to achieve a higher throughput performance and a substantial improvement of the dewatering effect would, however, lead to a doubling of the reversing forces given this single-mass system and, thus, would involve a load of 20 t on the bearings which would not only lead to difficult to control bearing loads but would also lead to a heavy weight design of the claimed structural elements which could not be economically justified.
In comparison thereto, the dual-mass vibrating screen resonance system is not limited by the height of the bearing loads but by the values of acceleration of the counter-mass which have a direct relationship to the operating mass. Given, for example, a vibrating screen centrifuge whose operating mass amounts to 0.4 t, a counter-mass of more than 8 t is required in order to absorb an axial acceleration of 20 g of the operating mass in order to keep the foundation forces small (for example, below 1 g). This not only leads to a cumbersome and excessively heavy design of the vibrating screen centrifuge but is also connected to an unnecessarily high outlay for material and capital costs.
German AS No. 1 167 750 discloses a vibrating screen centrifuge comprising two vibrating and rotating operating masses which are placed in vibration with a phase shift of 180.degree. in axial direction. The operating masses are thereby composed of two screen drums arranged following one another in axial direction having different angles of inclination which are vibrationally connected to one another via spring elements in an elastic fashion. Disadvantageous in this known vibrating screen centrifuge, however, is that the screen drums arranged following one another and vibrationally elastically connected to one another must be exactly mated to one another in terms of weight and the operation of these two operating masses can only be maintained at a specific frequency. Moreover, even slight modification in the quantity of material delivered, in the composition and/or in the dampness of the charging stock to be dewatered lead to considerable developments of unbalance in the vibrating and rotating operating masses which are transmitted onto the supporting bearings in the form of tilt moments and must be absorbed by these. This in turn requires a high-strength design of the bearings carrying the screen drums arranged in tandem, their useful life being extremely low due to the high stresses.
The object of the invention is to create a vibrating screen centrifuge for dewatering fine-grained material which, while avoiding all of the disadvantages recited above, enables a substantial increase in the separating effect and in the throughput performance in addition to enabling a compact and lightweight structure.
This object is achieved in that both operating masses are held on one and the same rotationally seated element by means of their vibrator springs, each of the two masses being separately in communication with a drive. Achieved in a very advantageous way by means of this inventive design of the vibrating screen centrifuge is that with the opposite vibration of the two operating masses, the mass forces in the final positions of the vibrations mutually cancel, so that mass forces are not transmitted onto the bearings of the drive masses either during the axial acceleration in the start-up phase or operation of the centrifuge. The axial and rotational acceleration of the operating masses can, therefore, be quite substantially increased in comparison to known vibrating screen centrifuges having a conventional design of the supporting bearings, thus leading to an improvement of the separating efficiency and to a noticeable increase in the throughput performance. The vibrating screen centrifuge of the invention is also completely unaffected by modifications in the quantity of material delivered, of the material composition and/or of the moisture content in the charging stock. Moreover, a particularly compact and lightweight structure of the vibrating screen centrifuge is achieved by means of these features of the invention.
In a further development of the invention, the vibrator springs connecting the two operating masses are fashioned as rubber members having sheet steel plates lying therebetween, these being arranged uniformly distributed over the circumference of the rotational drive shaft and being arranged in a radial direction. In comparison to steel springs, rubber springs are distinguished particularly by their simple, compact structure and high service life.
In accord with a further, advantageous development of the invention, the rubber members are rectangular and are mutually arranged uniformly distributed over the circumference by means of clamping wedges. With the assistance of the clamping wedges, not only can the rubber members be advantageously rigidly clamped relative to one another, but they can also be provided with a pre-stress necessary for optimum operation.
In accord with a further advantageous development of the invention, a double crank drive is provided as a vibrational drive, this being coupled via spring elements to the vibrating and rotating operating masses. The assistance of the double crank drive advantageously achieves a compulsory excitation of the two operating masses vibrating relative to one another. As a result of the coupling of the double crank drive to the vibrating and rotating operating masses via spring elements, the start-up of the vibrating screen centrifuge to the operating speed is quite substantially facilitated in a very advantageous way.
In a further development of the invention, a tumbling drive can be used as vibratory drive as warranted in a very advantageous way, this being coupled via elastic spring elements to the two vibrating and rotating operating masses. The tumbling drive is particularly distinguished by its extremely simple design and compact structure.
In an advantageous development of the invention, the two vibrating and rotating operating masses are composed of a materials distributor which is expanded funnel-like toward the top and of a screen basket which is inverted over the materials distributor at a distance and is expanded funnel-like in a downward direction. An especially stout and compact structure of the vibrating screen centrifuge is thus achieved.
In order to achieve optimum vibrating conditions, the two vibrating and rotating operating masses are fashioned about equal in weight in terms of their weight in accord with a further, preferred development of the invention.
Other objects, advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiment in the specification, claims and drawings, in which: